Scintillation recording device for producing both black and white and multi-color photographic records

ABSTRACT

The output of a scintillation probe is connected to energize one or more level discriminators, which respond to different levels of radioactivity detected. Each level discriminator is connected to permit energization of a different colored light source, the light from which exposes a color-sensitive photographic film.

United States Patent Brunnett et al.

[ Aug. 8, 1972 [54] SCINTILLATION RECORDING DEVICE FOR PRODUCING BOTH BLACK AND WHITE AND MULTI-COLOR PHOTOGRAPHIC RECORDS Inventors: Carl J. Brunnett, Mayfield Heights; Donald C. Payne, Willoughby, both of Ohio [73] Assignee: Picker Corporation, White Plains,

Filed: Aug. 15, 1967 Appl. No.: 660,823

[52] US. Cl. ..250/71.5 S, l78/6.7 R, l78/7.86,

250/65 R, 250/227 Int. Cl. ..G0lt1/20 Field of Search.....250/7l.5, 71.5 S, 71, 80, 227,

250/65 R; l78/6.7 R, 6.7 A, 7.86

[56] References Cited UNITED STATES PATENTS 3,549,887 12/1965 Hansen ..250/71 R X 3,004,101 10/1961 Jacobs et a1 ..250/65 UX 2,593,925 4/1952 Sheldon ..250/71.5 S UX 2,776,377 1/1957 Anger ..250/71.5 S 3,159,744 12/1964 Stickney et al. ..250/7 1 .5 3,303,508 2/1967 Jaffe et al. ..250/71.5 S

Primary Examiner1ames W. Lawrence Assistant Examiner-Morton J. Frome Att0rneyWatts, Hoffmann, Fisher and Heinke [57] ABSTRACT The output of a scintillation probe is connected to energize one or more level discriminators, which respond to different levels of radioactivity detected. Each level discriminator is connected to permit energization of a different colored light source, the light from which exposes a color-sensitive photographic film.

9 Claims, 5 Drawing Figures DISCRIMINATING AMPLIFIER /I2 RATE T0 METER STYLUS o VARIABLE-GAIN ONE SHOT AMPLIFIER 24 MULTIVIBRATOR PATENTEDAUG 8 I972 3,683,184

E SHOT fie AMPLIFIER 24 MUU' I VIBRATOR swam I l FILM 4o 36 F 54 4s -5 NORMALIZING AMPLIFIER G PI L U Y [6O 0- IOO /o 4 II LEVEL LEVEL CONTRAST DERANDOM'ZER a DISC. DISC. ENHANC. I To O-I7%,67-IOO/., 34 s4% o--5o% CONTROL IL -r\ I r I r I r SPEED /72 GATE GATE GATE CONTROL I/ I/ I LIGHT LIGHT LIGHT SOURCE SOURCE SOURCE GREEN FILTER/ I INVENTORS CARL J. BRUNNETT DONALD C. PAYNE ATTORNEYS PATENTEDMIE 1912 3.683; 184

sum 3 or 3 FROM I4 352 354 356 362 TO 64,66,66 FROM l6 MV f MV 358 7" 350 1 366A FROM 72 i Fig. 5 INVENTORS CARL J. BRUNNETT BY DONALD c. PAYNE WW $W a M A T TORNE YS SCINTILLATION RECORDING DEVICE FOR PRODUCING BOTH BLACK AND WHITE AND MULTI-COLOR PHOTOGRAPHIC RECORDS BACKGROUND OF THE INVENTION 1. Field of the Invention.

This invention relates to scintillation scanning of radioactive isotope concentration and distribution, and, more. particularly, to a scintillation recording device for producing a multi-colored photographic record.

Scintillation scanning is used in modern medical techniques for the diagnosis of certain types of ailments, such as the presence of malignant or benign tumors. In using a scintillation scanning technique, a quantity of radioactive isotope is administered to a patient. The administered isotope collects in certain organs of the patients body, such as his liveror spleen. The quantity and distribution of the radioactive energy in the organ under study is then measured and recorded, so that a radiologist or physician may determine the location and extent of the malformation within the organ.

2. Descriptionof the Prior Art.

Various devices have been proposed for accomplishing scintillation scanning and recording. One successful scintillation scanner is described in US. Pat. No. Re 26,014, issued May 3, 1966 to J. B. Stickney et al., and assigned to the assignee of the present invention. When utilizing that device, a scintillation probe is positioned over the area of a patients body to be investigated. The probe is then caused to move back and forthover the patient in a series of spaced rectilinear paths until a graphic representation of the distribution of isotope in the investigative area has been produced.

In the device of the Stickney et al. patent, the scintillation probe is mechanically and electrically connected to a suitable dot recording mechanism for producing one type of permanent graphic image. The probe is also electrically and mechanically connected to a light source, such as a cathode ray tube. The latter electrical connection is described in detail in US. Pat. No. 3,159,744, issued Dec. 1, 1964 to J. B. Stickneyet al., and assigned to the assignee of the present invention. In the device described in the latter patent, the light source produces light pulses which vary both in frequency and in intensity in accordance with the amount of radioactivity detected to provide what has become known as enhancement or contrast enhancement. The light pulses expose photographic film to produce a graphic display of the distribution of the isotope in the area under investigation, with areas having the greater radioactivity producing lighter images on the negative film than areas of lesser radioactivity.

More recently, various proposals have been made to produce multi-colored graphic displaysof the distribu- The production of an image on color-sensitive photographic film has also been proposed. According to the latter proposal, a group of color filters is coupled to a servo-mechanism .and positioned between a light source (cathode ray tube) and a color-sensitive film. The servo-mechanism shiftsthe filters in response to the amount of radioactivity detected. The latter device, although quite successful, does involve moving parts to mechanically position the various filters in front of the spot ;on the cathode ray tube face. This may be somewhat disadvantageous from the point of view of exact positioning of the filters and obtaining a clear line of demarcation when shifting from one filter to another. The present invention obviates this disadvantage by providing apparatus wherein the change from one color of light to another impinging on the color-sensitive film is controlled electronically, and wherein the only mechanical movement required is that necessary to coordinate movement of the scanning head and movement of the colored light spot with respect to the color-sensitive film. Thus the speed of response is greatly increased.

The useof colored images in scintillation studies has several advantages. One advantage is that a color image facilitates diagnosis of a patients alirnent by a radiologist or other specialist performing the study, and is especially useful to surgeons-andother physicians who are not as skilled as the specialist in analyzingthe information obtained from such astudy. While various shades of gray in a black and white image may be difficult to separate from each other, the used amulticolored image accentuates changes in'radiation intensity shown by different colors in various parts of the image.

SUMMARYOF THE INVENTION A device embodying the present invention provides both a conventional black and white photographic image of radiation distribution of an area under study, as well as a multi-colored image of the area. The black and white image is provided by means of the circuitry described in the aforementioned US. Pat. No. 3,159,744, whereas the multi-colored image is obtained by utilizing three primary colors of light singly or in various combinations. to produce six different colors to expose a color-sensitivephotographic film. A signal whose amplitude is proportional to the intensity of radiation detected by the scintillation probe as it scans across an area under investigation, is provided as input to a plurality of level discriminators. The level discriminators are preset to be actuated when the input signal thereto reaches certain percentages of itsmaximum range of possiblearnplitudes, andto be unactuated when the input signal is within other amplitude ranges. Each level discriminator controls the energization of a different one of a plurality of light sources,

I three sources of white light being provided in the present instance. Each'of the sources of white light has positioned adjacent thereto a filter for transmitting light of a different color, the transmitted light being one or a combination of the three primary colors red, green,.and blue. The light passing through the three filters is fed through a fiber optic :system and caused to impinge at one spot on a color-sensitive film.

As in the prior art, signals are produced in the device whenever the radiation detected by the scintillation probe exceeds a given predetermined value, and the repetition rate of the signals is dependent upon the intensity of the radiation detected. In the black and white image produced, this feature is necessary in order to increase the density of the image in those areas where the radiation intensity is greatest. In the present case where a colored image is also produced, the change in density is no longer required in the colored image.

One of the features of the present invention is the provision of circuitry to prevent the dots making up the colored image from overlapping, which could produce annoying dark spots on the color-sensitive film.

Another feature of the invention lies in the provision of a contrast enhancement control, whereby the range of radiation may be compressed so that the six available colors recorded on the film cover a range of as little as 50 percent of the normal radiation intensity range that may be recorded. For example, it may be that an area of a patients body under study may emit radiation of 20 considerable intensity but varies from its maximum to minimum values over only 50 percent of the maximum utilizable range. The contrast enhancement control may then be adjusted so that all six available colors are utilized within that 50 percent range rather than only one or two colors being available.

Further features and advantages of the invention will become apparent from the following description of one embodiment thereof, taken in conjunction with the accompanying drawings, in which:

DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a device embodying the invention;

FIG. 2 is a circuit diagram of the level discriminators embodied in the device shown in FIG. 1;

FIGS. 3 and 4 are circuit diagrams of the speed control and the normalizing amplifier, respectively, embodied in the device of the invention; and,

FIG. 5 is a logic diagram of the derandomizer utilized in the device shown in FIG. 1 to prevent the overlapping of colored light pulses on the color-sensitive film.

DESCRIPTION OF THE PREFERRED EMBODIMENT Inasmuch as the preferred embodiment of the invention utilizes the circuitry described in the aforementioned US. Pat. No. 3,159,744, that portion of the device of the present invention will be described only briefly herein. Reference may be made to that patent for a more complete description of the various elements.

FIG. 1 illustrates in block diagram form a device embodying the present invention. As shown, scintillation responsive means such as a conventional scintillation probe provides output signal pulses in response to radiation detected by the probe. The signal pulses from the probe 10 are provided to a discriminating amplifier 12. The discriminating amplifier 12 is of conventional type, and amplifies each pulse received from the probe 10 to provide one amplified pulse for each radioactive impulse detected by the probe 10 and falling within a preselected pulse height range. The output of the discriminating amplifier 12 is connected to a stylus (not shown) to produce a graphic image on a sheet of paper in a conventional well-known manner. The output of the amplifier 12 is also connected to the input of a rate meter 14 and the input of a one-shot multivibrator 16.

The rate meter 14 is of conventional type which detects and indicates the rate of signal pulses. A range control switch 18 is provided for selecting an appropriate scale on a meter dial 20. A time constant selector switch 22 is also provided for selecting the length of time over which the signal pulse rate is measured to determine the rate. The longer the time constant, the more stable will be the reading on the dial 20. Any change in the pulse rate will be reflected by the output of the rate meter, but that output will lag the actual change by a length of time proportional to the time constant selected.

The output of the rate meter 14 is connected to the input of a variable-gain, direct-coupled amplifier 24, whose output signal level lies within a certain predetermined range at all times.

The output of the variable-gain amplifier 24 is connected to the input of the power supply 26. The varying output signal of the variable-gain amplifier 24 controls the power supply 26, and causes its output voltage to vary proportionally with the variable-gain amplifier output and therefore with the probe signal pulse count rate.

The power supply 26 is conventional in design, and its output is connected to an accelerating ring or electrode 28 of a cathode ray tube, shown generally at 30. The output of the power supply 26 is also connected to ground through series-connected resistors 32, 34. The cathode ray tube 30 has a focusing electrode 36, which is connected to the juncture of the resistors 32 and 34.

The one-shot multivibrator 16, whose input is connected to the output of the discriminating amplifier 12, is of a type which will emit one impulse of a predetermined time duration and power for each signal pulse transmitted to it by the discriminating amplifier 12. The one-shot multivibrator 16, which is of conventional design, preferably includes an adjustment to vary the time duration of its output pulses.

The output of the one-shot multivibrator 16 is connected through a coupling capacitor 38 to a control grid 40 of the cathode ray tube 30. The control grid 40 is grounded through a resistor 42. The cathode ray tube 30 is also provided with a cathode 44, which is connected to the output of a 35-volt direct-current power supply 46. The connections of the control grid 40 and the cathode 44 of the cathode ray tube differ slightly from those set forth in the referenced US. Pat. No. 3,159,744. In the patent, the control grid is shown at ground potential and the output of the one-shot multivibrator is connected to the cathode. However, the operation of the cathode ray tube 30 is essentially the same as that described in the referenced patent. The cathode ray tube 30 also includes the usual phosphorescent or fluorescent screen 48, the light from which is focused to an appropriately sized dot by a collimater 50 for impingement on a black-and-white photographic film 52.

As is more fully described in the referenced patent, once the discriminated level of radiation activity is obtained, one light impulse will be emitted by the cathode ray tube 30 for each count detected by the probe 10 and passed by the discriminating amplifier 12. The intensity of the emitted light pulse will vary with the signal pulse count rate, because the voltages on the accelerating electrode 28 and on the focusing electrode 36 of the cathode ray tube vary with the count rate. Thus, the intensity of the light incident on the film 52, and hence the density of the image created thereon, in any given spot will reflect the signal pulse count rate in a corresponding spot in the area being studied. Since the probe 10 and the cathode ray tube 30 are mechanically connected together and move together as a scan is conducted, the resultant film exposure is a graphic reproduction which outlines the distribution pattern of the radiation and the concentration of radioactivity in the area under study.

The variable output signal of the rate meter 14 is connected to the input of a normalizing amplifier 54. The function of the normalizing amplifier 54 is to provide an output signal whose amplitude level varies over a predetermined amplitude range in response to an input signal from the rate meter 14 that may vary over a different amplitude range. In the present case, for example, the input signal from the rate meter 14 may vary from 5 volts to a more negative voltage not exceeding -10 volts. The normalizing amplifier 54 is so adjusted that its output signal varies from 5 volts to l volts over the entire amplitude range of the input signal.

The normalizing amplifier 54 is also provided with a contrast enhancement control 56, whose function is to raise the transition points at which the level discriminators (to be later described) operate. This merely compresses the range of radiation intensity being studied. Were the contrast enhancement control not provided, it is possible that in certain studies there would be so little difference in the various amounts of radiation received that only one or two of the six availablecolors would be present in the colored image. By setting the contrast enhancement control, the rangemay be compressed so that all six colors are available to indicate radiation variations over a smaller range.

The output signal from the normalizing amplifier 54 isprovided as an input signal to a plurality of level discriminators 58, 60, 62. The level discriminators 58, 60, 62 are preset to be actuated when the input signal to the discriminators reaches predetermined amplitude levels and to be unactuated when the input signal amplitude levels are less than or greater than predetermined values. In the present case, wherein three level discriminators are utilized, the discriminator 58 is actuated when the input signal thereto lies between 0 percent and 50 percent of its maximum amplitude range. In other words, if the input signal from the normalizing amplifier 54 ranges from volts to l0 volts, the discriminator 58 is actuated by a signal whose amplitude is between --5 volts and -7.5 volts. The level discriminator 60 responds to an input signal which lies within an amplitude range of 34 to 84 percent of the maximum range of -5 volts to volts, and the level discriminator 62 responds to a signal lying within an amplitude range of 0-17 percent and 67-100 percent of the maximum amplitude range. Thus, if the input signal to the level discriminators falls within the 0-17 percent amplitude range, the discriminators 58 and 62 are actuated; if the signal falls within the range of 17-34 percent, the discriminator 58 is actuated; if the signal falls within the range of 34-50 percent, the discriminators transition points may be varied as desired, and the levels referred to herein are used only by way of exampie.

The output signals from the level discriminators 58, 60, 62 are respectively provided as inputs to AND- gates 64, 66, 68. Input signals are also provided to the gates 64, 66, 68 from a derandomizer 70. The input to the derandomizer is connected to the output of the one-shot multivibrator 16 to receive a pulse of uniform height and width each time a signal pulse is provided from the discriminating amplifier 12 to the multivibrator.

The derandomizer 70 comprises logic means to prevent the overlapping of dots in the colored image, which might result in producing dark spots on the color-sensitive film. To this end, it is necessary that a gating pulse from the derandomizer 70 be present at the inputs of the gates 64, 66, 68 before a signal from the level discriminators 58, 60, 62 can be passed by the gates. The maximum rate of the pulses from the derandomizer to the gates is controlled by a speed control 72, which is manually set to correspond to the speed of scan of the probe 10. If desired, the derandomizer and speed control may be omitted and the output of the multivibrator 16connected directly to the gates 64, 66, 68. In that case, overlapping of dots may be prevented by scaling down the pulse input rate or by limiting the width of the dots.

If signals are simultaneously received by the gate 64 from the derandomizer 70 and from the level discriminator 58,.the gate 64 is enabled and a light source 74 is energized. Similarly, the gate 66 is enabled when signals are simultaneously received from the derandomizer 70 and from the level discriminator 60, and the gate 68 is enabled when signals are simultaneously received from the derandomizer 70 and from the level discriminator 62. When the gates 66 and 68 are enabled, they permit energization of light sources 76 and 78,respectively. The light sources 74, 76, 78 are identical to each other, and provide essentially white light output. Suitable light sources are available from Sylvania Electric Products, Inc. and are marketed by them as Model Rl 131C known as a Glow Modulator. This particular light source, while not the only one that may be utilized in the device embodying the invention, has an advantage in that it can be pulsed on and off at a high rate of speed.

The light sources 74, 76, 78 are respectively provided with filters 80, 82, 84. In the present application, the filter 80 is red, the filter 82 is blue, and the filter 84 is green. The filters 80, 82, 84 are of conventional Wratten type and may be obtained from the Eastman KodakCompany, of Rochester, New York. Light transmitted through the filters 80, 82, 84 passed through light pipes 86, 88, respectively, each of which consists of a series of parallel light-transmitting fibers. The light pipes 86, 88. 90 constitute a fiber optic structure,

which conducts light and is also flexible. The light:

transmitted through the light pipes 86, 88, 90 passes through a suitable aperture 92a in a collimating device 92 and impinges on a sheet 94 of color-sensitive photographic film. The collimating device 92 is preferably connected mechanically to the probe 10, so that as the probe scans an area under study the collimating device scans across the film sheet 94. Alternatively, the device 92 may be fixed in position and the film moved.

The fiber optics system is shown as a preferred form of light transmitting means between the filters 80, 82, 84, but not as the only light transmission means usable. Alternatively, the light transmission means might consist of a mirror system, a lens system, or any other such system that will cause the light from the various filters to coincide over substantially the same area in a plane defined by the aperture 92a in the collimating device 92. Of course, the aperture 92a is variable in dimensions to determine the size of the spot or dot of light incident on the film sheet 94.

In the form of the invention shown and described, the color-sensitive film 94 is of negative type, which produces a color that is complementary to the color of the light exposing the film. Such a film is available commercially from Eastman Kodak Company under the name Ektacolor film. It is apparent that the invention is not limited to the use of a negative type film, and a positive type film may be used if desired. Of course, when a negative type color-sensitive film is employed, to produce the desired color in the film, it must be exposed with light of a complementary color. For example, in order to produce cyan in the film, it must be exposed with red light; to produce magenta in the film, it must be exposed with green light; and to produce yellow in the film, it must be exposed with blue light. If a positive type color-sensitive film is employed, it is exposed with the color of light that it is desired to have in the colored image. I

The following table shows the various colors produced in a negative color-sensitive film in response to various combinations of colored light incident thereon in response to various input signal levels to the level discriminators:

COLOR OF NEGATIVE FILM blue through cyan and green to yellow and thence to red and magenta. Thus the red and green areas of confusion are separated by yellow, which is clearly distinguishable from blue by the ordinary color blind person. Of course, if the viewers color blindness is of the monochromatic type, he will see all colors as various shades of gray and the colored photographic image will be of little assistance to him over the black and white image.

If a positive color-sensitive film is being used, and the same arrangement of colors is desired on the film as in the case of a negative color-sensitive film, the light sources will have to be energized in a different order. In order to provide cyan, the blue and green sources must be energized; in order to provide yellow, the green and red sources must be energized; and in order to provide magenta, the red and blue sources must be energized. Such an adaptation is well within the skill of one versed in the art.

FIG. 2 is a circuit diagram of the level discriminators 58, 60, 62 and the gates 64, 66, 68. The input signal from the normalizing amplifier 54 (-5 volts to 10 volts) is connected by means of a terminal 96 to an input line 98 that feeds all three of the level discriminators.

As previously mentioned, in the example shown, the level discriminator 58 is actuated when the input signal from the normalizing amplifier 54 is between 0 and percent of its total range. Thus, if the total range of the input signal is from 5 volts to 10 volts, the level discriminator 58 is actuated when the signal is between 5 volts and 7.5 volts. As shown, the discriminator 58 comprises a difierential amplifier, shown generally by the numeral 100, which includes two PNP transistors 102, 104. The base of the transistor 102 is connected to the input line 98 through a resistor 106, and the emitters of the transistors 102, 104 are connected together and to ground through a resistor 108. The collectors of the transistors 102, 104 are respectively connected through load resistors 110, 112 to a 24 volt directcurrent supply (not shown). The base of the transistor Blue Cyan Green Yellow Red Magenta '5 Red (74 Red 74) Red 74 0 Blue (76) Blue (76) Blue (76) In Green (78) Green (78) Green (78) E .F." 0-1 INPUT SIGNAL LEVEL Attention is particularly drawn to the fact that the order in which the various light sources and their combinations there are utilized is designed to aid as much as possible a color blind person in distinguishing between the various colors representing radiation of different intensities. It is well known that a person suffering from dichromatism has his color perception reduced essentially to distinguishing between only yellows and blues. Most such persons confuse reds, greens and yellows of certain shades with one another, but never confuse the yellows and blues. Therefore, the order in which the various light sources are energized causes blue and yellow to be well separated, so that the usual color blind person can easily distinguish increases in radiation intensity as the film color progresses from is connected between the 24 volt supply and ground. The collector of the transistor 104 is also connected directly to the anode of a diode 116, whose cathode is connected to the base of an NPN-transistor 118. The base of the transistor 118 also is connected to the 24 volt supply through a resistor 120 having a relatively high resistance value. The transistors emitter is connected to the 24 volt supply through a load resistor 122, and its collector is grounded through a resistor 124. The collector of the transistor 118 is also connected directly to the base of a PNP-transistor 126 in the gate 64.

The gate 64 comprises the transistor 126, an NPN- transistor 128, and a PNP-transistor 130. The collector of the transistor 126 is connected through a load resistor 132 to the 24 volt supply, and the emitter of the transistor is connected to the cathode of a diode 134.

The anode of the diode 134 is connected to one end of a fixed resistor 136, whose other end is connected through a variable resistor 138 to the emitter of the transistor 128. The base of the transistor 128 is connected to the 24 volt supply through a resistor 140, and is also connected directly to the collector of the transistor 130. The collector of the transistor 128 is connected to a terminal 142 through a resistor 144. The terminal 142 is connected to one side of the light source 74 located behind the red filter 80 (FIG. 1), the other side of the light source being connected to a positive voltage source (not shown) through a terminal 145. When the transistors 128, 126 are conducting, current flows through the light source and through the transistors to the 24 volt supply. The variable resistor 138 serves as a brightness control for the light source 74. The base of the transistor 130 is connected to a ter minal 146 through a resistor 148, and the emitter of the transistor 130 is connected directly to ground. The terminal 146 is connected to receive negative gating pulses from the derandomizer 70 (FIG. 1) to cause the transistor 130 to conduct.

In the operation of the level discriminator 58, the transistor 104 is normally conducting, and the transistor 102 is normally non-conducting. This is accomplished by setting the movable arm of the potentiometer 114 so that a potential of approximately 7.5 volts is placed on the base of the transistor 104. Conduction of the transistor 104 causes a voltage drop across the resistor 1080f substantially 7.2 volts. Thus the emitter of the transistor 102 is negative with respect to the base of the transistor 102 until the input signal on the line 98 reaches approximately 7.5 volts going in a negative direction. When this occurs, the transistor 102 will start to conduct, which will increase the voltage drop across the resistor 108 and cause the transistor 104 to be cut off.

When the transistor 104 is conducting, the potential transferred from its collector through the diode 116 to the base of the transistor 118 is positive with respect to the potential of theernitter of the transistor 1 18. Therefore, the transistor 118 conducts. When the transistor 118 conducts, the potential on its collector is approximately 1 2 volts, which is transferred to the base of the transistor 126 in the gate 64. Thus, the base of the transistor 126 is negative with respect to the emitter and the transistor 126 will conduct if the transistor 128 is conducting. The transistor 128 will conduct when its base is positive with respect to its emitter. This condition occurs when the transistor 130 is conducting. The transistor 130 will conduct when a negative gating pulse is received from the derandomizer 70 and applied to its base. When the transistor 130 conducts, the base of the transistor 128 rises virtually to ground potential, which causes that transistor to conduct. Therefore, a current path is established from the terminal 74 through the transistors 128, 126, to the 24 volt supply to energize the lamp 74. An input signal to the level discriminator 58 of -5 volts to 7.5 volts must be received simultaneously with a negative pulse from the deran domizer 70 to the gate 64 in order to energize the light source 74.

When the input signal on the line 98 reaches or exceeds 7.5 volts in a negative direction, the transistor 102 conducts, which cuts off the transistor 104. The

collector potential of the transistor 104 drops to 24 volts, which potential is transferred to the base of the transistor 118. Thebase and emitter of the transistor 118 are now both at the same potential, and that transistor is cut off. When the transistor 118 is cut off, the potential of its collector rises to ground, which in turn cuts off the transistor 126 and breaks the current path from the terminal 142 to the 24 volt supply.

The level discriminator 60 and the gate 66, which permit energization of the light source 76 located adjacent the blue filter 82 (FIG. 1), are generally similar to the discriminator 58 and the gate 64 previously described. The level discriminator 60 differs from the level discriminator 58, however, in that it employs two differential amplifiers, indicated generally by the numerals 150, 152. The operation of the level discriminator 60 is different from that of the level discriminator 58, because the discriminator 60 actuates or opens the gate 66 when the input signal to the discriminator 60 is between 34 percent and 84 percent of the maximum input signal amplitude range.

The differential amplifier employs two PNP- transistors, 154, 156. The collectors of the transistors 154, 156 are respectively connected through load resistors 158, 160 to the 24 volt supply. The emitters of the transistors 154, 156 are connected together and to ground through a resistor 162. The base of the transistor 154 is connected through a resistor 164 to the input line 98. to receive the signal from the normalizing amplifier 54. The base of the transistor 156 is connected to the movable arm of a potentiometer 166, one end of which is connected to the 24 volt supply and the other end of which is grounded.

The second differential amplifier 152 is. very similar to the amplifier 150 and comprises two PNP-transistors 168, 170. The collectors of the transistors 168, are respectively connected through load resistors 172,174 to the 24 volt supply, and the emitters are connected together and to ground through a resistor 176. The base of the transistor 168 is connected through a resistor 178 to receive the input signal from the line 98. The baseof the transistor 170 is connected to the movable arm of a potentiometer 180, which serves as a voltage divider connected between the 24 volt supply and ground.

A pair of diodes 182, 184, have their cathodes respectively connected to the collectors of the transistors 156, 168. Theanodes of the diodes are connected together and to the base of an NPN-transistor 186. The base of the transistor 186 is connected to ground through a resistor 188 having a relatively high resistance. value, and the collector of the transistor 186 is connected to ground through a resistor 190. The emitter of the transistor 186 is connected to the juncture of resistors 192, 194 which form a voltage divider connected between the 24 volt supply and ground. The collector of the transistor 186 is also connected directly to the base of a PNP-transistor 196 in the gate 66.

Thegate 66 comprises the transistor 196, an NPN- transistor 198, and a PNP-transist-or 200. The collector of the transistor 196 is connected to the 24 volt supply through a load resistor 202, and the emitter is connected to the cathode of a diode 204. The anode of the diode 204 is connected to one end of a resistor 206,

the other end of which is connected to the emitter of the transistor 198 through a variable resistor 208, which serves as a light source brightness control. The collector of the transistor 198 is connected through a resistor 210 to a terminal 212. The light source 76 located behind the blue filter 82 (FIG. 1) is connected between the terminal 212 and a terminal 214 (positive voltage) to be energized when the transistors 196 and 198 are both conducting. The emitter of the PNP- transistor 200 is grounded, the collector is connected through a load resistor 216 to the source of 24 volts, and the base is connected through a resistor 218 to a terminal 220. Negative gating pulses are supplied to the terminal 220 from the derandomizer 70 to turn on and off the transistor 200.

In operation, the transistors 156 and 170 are conducting when the input signal received on the line 98 is at the zero end of the sigial amplitude. range, that is, at 5.0 volts. The movable arms of the potentiometers 166, 180 are set to provide appropriate negative voltages to the bases of the transistors 156, 170 to maintain them conducting until the input signals to the transistors 154, 168 reach predetermined percentage values of the maximum signal amplitude range. In the present example, it is desired to have the transistor 170 stop conducting when the input signal on the line 98 reaches 6.7 volts going in a negative direction, and the transistor 156 to stop conducting when the input signal reaches 9.2 volts. This is accomplished by appropriately setting the movable arms on the potentiometers 166, 180 to provide negative voltages on the bases of the transistors 156, 170 of approximately 9.2 volts and 6.7 volts, respectively.

Until the input signal on the line 98 reaches 6.7 volts increasing in a negative direction, the transistor 156 is fully conducting because its base is negative with respect to its emitter. The transistor 154 is non-conducting because of the negative potential on its emitter. Similarly, the transistor 170 is fully conducting, and the transistor 168 is cut off. When the transistor 156 is conducting, its collector voltage is approximately 14 volts. When the transistor 168 is non-conducting, its collector potential is at approximately 24 volts. A juncture point 222 between the anodes of the diodes 182, 184 assumes the most negative voltage present on the collectors of the transistors 156, 168. This voltage (24 volts) is connected to the base of the transistor 186 and maintains that transistor in a cutoff condition because its base is negative with respect to its emitter.

When the transistor 186 is cut ofi', its collector potential is at ground level to maintain the gate 66 closed and the light source 76 de-energized. This occurs because, when the base of the transistor 196 is at ground potential, that transistor is non-conducting. Even though a negative pulse is received from the derandomizer on the terminal 220, and the transistor 200 becomes conductive, the light source 76 will remain un-energized because there is no path from the terminal 212 to the 24 volt source.

When the input signal applied to the base of the transistor 168 from the input line 98 reaches the predetermined level of 6.7 volts (34 percent of the signal amplitude range), the base of the transistor 168 becomes negative with respect to its emitter and the transistor is turned on. When the transistor 168 is turned on, the transistor 170 turns off. The voltage at the juncture point 222 rises to approximately -l4 volts, which makes the base of the transistor 186 positive with respect to the transistor emitter. The transistor 186 is thus turned on, and the potential of its collector and the base of the transistor 196 falls below ground level to approximately -l4 volts. Because the emitter of the transistor 196 is positive with respect to its base, the transistor 196 will conduct if the transistor 198 is conducting, which in turn will occur when the transistor 200 is conducting. The transistor 200 will conduct when a negative pulse is received at the terminal 220 from derandomizer 70, and will make the base of the transistor 198 positive with respect to the transistor emitter. A circuit is then completed through the light source 76 connected between the terminals 212, 214 and through the transistors 198, 196 to the 24 volt supply to energize the light source.

The current path for the light source 76 will be broken if current flow through the transistor 200 is interrupted by the absence of a negative gating pulse from the derandomizer or if current flow through the transistor 196 is interrupted due to non-conduction of the transistor 186 in the level discriminator 60. The latter will occur when the input signal on the line 98 reaches the predetermined amplitude level of 9.2 volts (84 percent of the signal amplitude range). When the input signal reaches that predetermined level going in a negative direction, the base of the transistor 154 becomes negative with respect to the transistor emitter. The transistor 154 then conducts, which cuts off current flow through the transistor 156. The collector of the transistor 156 then drops to 24 volts, which is transferred through the diode 182 to the base of the transistor 186. The base of the transistor 186 is then negative with respect to the potential of the transistor emitter, and current flow through the transistor 186 is cut ofi. This condition exists until the input signal to the discriminator is reduced below the 84 percent level, at which time the transistor 156 will again conduct and cause the transistor 186 to conduct. During the time that the input signal exceeds 84 percent of the signal amplitude range, the transistor 168 remains in a conductive state and the transistor 170 is cut off.

To recapitulate briefly, when the input signal level to the level discriminator 60 ranges from 5 volts to 6.7 volts (0-34 percent of the signal amplitude range), the transistors 154 and 168 are cut ofl, the voltage on the base of the transistor 186 is approximately 24 volts and the transistor 186 is non-conductive. When the voltage level of the input signal lies between 6.7 volts and 9.2 volts (34-84 percent of the input signal range), the transistors 154 and 170 are non-conductive, and the transistors 156 and 168 are conductive. The voltage at the base of the transistor 186 is approximately 14 volts, and the transistor 186 is conductive. When the input voltage from the line 98 exceeds 9.2 volts in a negative direction (84-100 percent of the signal amplitude level), the transistors 154 and 168 are conductive, and the transistors 156 and 170 are nonconductive. This causes the potential at the base of the transistor 186 to again fall to 24 volts to cut ofl that transistor. It is now apparent that the light source 76 connected between the terminals 212 and 214 can be energized only when the input signal level on the conductor 98 lies between 6.7 volts and 9.2 volts, that is, between 34 percent and 84 percent of the input signal amplitude range.

The level discriminator 62 is very similar to the level discriminator 60 just described, except that the discriminator 62 is actuated to open the gate 68 when the input signal level lies between and 17 percent of the signal amplitude level range and again when it lies between 67 percent and 100 percent of the signal level range. Again, the discriminator 62 includes two differential amplifiers, indicated generally by the nu merals 230 and 232.

The differential amplifier 230 comprises a pair of PNP transistors 234, 236. The collectors of the transistors 234, 236 are respectively connected through load resistors 238, 240 to the 24 volt supply. The emitters of the two transistors are connected together and to ground through a resistor 242. The input signal from the normalizing amplifier is supplied from the line 98 to the base of the transistor 234 through an input resistor 244. A potentiometer 246 is connected between the 24 volt supply and ground and its movable arm is connected directly to the base of the transistor 236 to provide a predetermined negative potential on the transistor base.

The differential amplifier 232 comprises a pair of PNP transistors 248, 250. The collectors of the transistors 248, 250 are respectively connected through load resistors 252, 254 to the 24 volt source, and the emitters of the transistors are connected together and to ground through a resistor 256. The base of the transistor 248 is connected to the input line 98 through an input resistor 258. The base of the transistor 250 is connected to the movable arm of a potentiometer 260, which is connected as a voltage divider between the 24 volt supply and ground to provide a predetermined negative potential on the transistor base.

The collectors of the transistors 236, 248 are respectively connected to the anodes of diodes 260, 262. The cathodes of the diodes 260, 262 are connected to a juncture point 264, which is connected to the 24 volt supply through a resistor 266 and is connected directly to the base of an NPN-transistor 268.

The emitter of the transistor 268 is connected to the 24 volt supply through a resistor 270. The collector of the transistor 268 is connected to ground through a resistor 272, and is also connected directly to the base of a PNP-transistor 274 in the gate 68. The state of the transistor 268 in the level discriminator 262 controls the opening and closing of the gate 68, disregarding for the moment the presence or absence of a negative pulse from the derandomizer 70 applied to the gate 68.

The gate 68 comprises the transistor 274, an NPN- transistor 276 and a PNP-transistor 278. The collector of the transistor 274 is connected to the 24 volt supply through a resistor 280. The emitter of that transistor is connected to the cathode of a diode 282, whose anode is connected to one end of a fixed resistor 284. The other end of the resistor 284 is connected through a variable resistor 286 to the emitter of the transistor 276. The collector of the transistor 276 is connected to a terminal 288 through a resistor 290. The light source 78 located adjacent the green filter 84 (FIG. 1) is connected between the terminal 288 and a positive terminal 292. The variable resistor 286 serves as a brightness control for the light source 78 when the transistor 274 is conducting. The base of the transistor 276 is connected to the 24 volt supply through a resistor 294 and is connected directly to the collector of the transistor 278. The emitter of the transistor 278 is grounded, and its base is connected through a resistor 296 to a terminal 298 to receive negative gating pulses from the derandomizer 70.

The gate 68 operates in the same fashion as the gates 64 and 66 previously described, and its operation will not be described in detail. It is sufficient to note that a conductive path will be established from the terminal 288 to the 24 volt supply if the transistors 274, 276 are both conducting. The transistor 274 will be conductive if the transistor 268 in the level discriminator 62 is conducting. If the transistor 268 is cut off the potential on the base of the transistor 274 will rise to ground level and cause that transistor to be cut ofi. Also, if the transistor 278 is cut off due to the absence of a negative input pulse at the terminal 298, the potential on the base of the transistor 276 will drop to-24 volts and cause that transistor to be cut off. Thus, it is seen that the transistors 268, 274, 276, 278 must all be conducting in order for the light source 78 to be energized.

In order for the level discriminator 62 to operate in the desired manner, the transistor 268 must be conducting when the input signal level on the line 98 lies between 5 volts and 5.8 volts (between 0-17 percent of the signal amplitude range). The transistor 268 must be non-conductive when the input signal level lies between 5.8 volts and 8.4 volts, and must be conductive again when the input signal level lies between 8.4 volts and 10 volts (between 67 100 percent of the input voltage signal range). In the example being described, the movable arm of the potentiometer 246 is set to provide a potential of 5.8 volts on the base of the transistor 236, and the movable arm of the potentiometer 260 is set to provide potential of -8.4 volts on the base of the transistor 250. Until the input signal applied to the base of the transistor 234 in the first differential amplifier 230 exceeds -5 .8 volts in a negative direction, the transistor 234 is non-conducting and the transistor 236 is conducting. During that time, the transistor 248 is non-conducting and the transistor 250 is conducting. The collector of the transistor 236 is at approximately 14 volts when that transistor is conducting, and the collector of the transistor 248 is at 24 volts when that transistor is non-conducting. The juncture point 264 is at the more positive of the potentials of the collectors of the transistors 236, 248. A potential of 14 volts is therefore applied to the base of the transistor 268, which causes the transistor 268 to conduct. The collector of the transistor 268 is at approximately --l4 volts, which causes the transistor 274 to become conductive.

When the input signal level on the base of the transistor 234 reaches 5.8 volts going in a negative direction, the transistor 234 becomes conductive and the transistor 236 is cut off. The transistor 248 remains cut off and the transistor 250 remains in a conductive state. This causes the voltage at the juncture point 264 and at the base of the transistor 268 to drop to 24 volts, which cuts off the transistor 268. The collector voltage of the transistor 268 rises: to ground level and cuts off the transistor 274 in the gate 68. The circuits remain in this condition until the input signal level applied to the base of the transistor 248 reaches 8.4 volts going in a negative direction. When that level is reached, the transistor 248 becomes conductive, and cuts off the transistor 250. The transistor 234 remains in a conductive state and the transistor 236 remains in a non-conductive state. The juncture point 264 and the base of the transistor 268 assume the voltage at the collector of transistor 248(14 volts) and the transistor 268 again becomes conductive. The potential of the collector of the transistor 268 drops from ground level to approximately 14 volts, which causes the transistor 274 in the gate 68 to turn on. The circuits remain in this condition throughout the remainder of the 67-100 percent input signal amplitude range.

Briefly, when the input signal level to the level discriminator 62 ranges from 5 volts to 5.8 volts (-17 percent of the signal amplitude range), the transistor 236 is conducting, the voltage applied to the base of the transistor 268 is approximately l4 volts, and the transistor 268 is conducting. When the voltage level of the input signal lies between 5.8 volts and 8.4 volts, the transistor 236 is cut off. The voltage applied to the base of the transistor 268 drops to 24 volts, and that transistor is cut off. When the input voltage from the line 98 exceeds 8.4 volts in a negative direction (67-100 percent of the signal amplitude range), the transistor 248 becomes conductive, which causes a potential of approximately 14 volts to again be applied to the base of the transistor 268. This causes the transistor 268 to again become conductive and applies approximately l4 volts to the base of the transistor 274 to cause it to become conductive. The light source 78 will be energized only when a negative gating pulse is received at the terminal 298 from derandomizer 70 and an input signal is simultaneously received from the normalizing amplifier 54 which lies within the ranges of 0-17 percent and 67-100 percent of the input signal amplitude range.

It is pointed out that more than six output colors may be obtained by utilizing more than one level discriminator in conjunction with each light source. If more than one discriminator is utilized with one light source, each discriminator would control a separate switching transistor to provide more than one level of current flow through the corresponding source of-monochromatic light. For example, if the green and blue sources provide equal intensity light, the combination will produce cyan light. If then, the intensity of the green light is increased, the light output of the two sources will tend toward green rather than be true cyan. Of course, such additional level discriminators could be provided almost indefinitely to produce virtually a continuous spectrum of output light. However, it has been found that one or two intensity levels of the three primary light sources provide sufficient output colors for normal analyzing purposes.

It is also pointed out that all three sources may be illuminated simultaneously at equal intensity levels to provide white light. This may be done manually or automatically.

The normalizing amplifier 54 shown in FIG. 1 is essentially a direct-current amplifier, whose function is to provide output signals whose amplitudes vary over predetermined range in response to input signals from the rate meter 14 that may vary over a different range of amplitudes. As shown in the schematic diagram of FIG. 4, input signals from the rate meter 14 are supplied to a terminal 300, which is connected through an input resistor 302 to the base of a PNP transistor 304. In the present case, the arrangement is such that input signals from the rate meter 14 may vary in amplitude from 5 volts to a more negative voltage not exceeding volts. The collector of the transistor 304 is connected in series through a fixed resistor 306 and a variable resistor 308 to the 24 volt supply. The variable resistor 308 serves as a gain control for the amplifier. The emitter of the transistor 304 is connected through a resistor 310 to the movable arm of a potentiometer 312. The ends of the potentiometer 312 are respectively connected to ground and to a direct-current supply of 6 volts. The potentiometer 312 serves as a zero adjustment control for adjusting the amplifier to provide an output signal of 5 volts, when the input signal from the rate meter 14 is 5 volts.

The collector of the transistor 304 is also directly connected to the base of an NPN-transistor 314. The emitter of the transistor 314 is connected through a resistor 316 to the 24 volt supply. The collector of the transistor 314 is connected through a fixed resistor 318 to the movable arm of a potentiometer 320. One end of the potentiometer 320 is connected to ground and the other end is connected to the 6 volt supply. The potentiometer 320 serves as the contrast enhancement control, previously referred to in connection with FIG. 1 and designated 56 in that figure.

The collector of the transistor 314 is also connected directly to the base of a PNP-transistor 322, whose collector is connected directly to the 24 volt supply. The emitter of the transistor 322 is connected to ground through a fixed resistor 324, and is also connected directly to an output terminal 326 to supply a signal to the level discriminators 58, 60, 62 previously described.

The 5 volt starting point of the output signal amplitude range is provided by the voltage drop across a resistor 328, one end of which is grounded and the second end of which is connected to the anode of a diode 330. The cathode of the diode 330 is connected directly to the 6 volt supply. The second end of the resistor 328 is also connected in series through a meter 332, a fixed resistor 334 and a variable resistor 336 to the output terminal 326. The variable resistor 336 serves as a meter calibration adjustment to adjust the meter at its full scale reading. The dial of the meter 332 may be calibrated in terms of percent of output signal amplitude range or in terms of color of energized light sources. The purpose of the diode 330 is to compensate for the base-to emitter drop of the transistor 322. A diode 338 is connected across the meter 332 with its anode connected to the resistor 334 and its cathode connected to the anode of the diode 330. The purpose of the diode 338 is to prevent excess reverse current from flowing through the meter 332 when the transistor 332 is in a non-conducting state.

In operation, the potentiometer 312 is first adjusted to provide a 5 volt output signal at the terminal 326 when the input signal received at the terminal 300 is -5 volts and the arm of the potentiometer 320 is set at 6 volts. In other words, the potentiometer 312 is adjusted so that the transistor 304 is just non-conductive when the input signal to its base is volts, which maintains the transistor 314 in a non-conductive condition. The emitter of the transistor 322 and the output terminal 326 are at a potential of approximately 5 volts. If it is desired to have the amplitude range of the input signal from the rate meter 14 provide a corresponding proportionate amplitude range of the output signal from the amplifier, the arm of contrast enhancement potentiometer 320 is set to provide 6 volts on the base of the transistor 322. The emitter of the transistor 322 is at 5 volts and hence the terminal 326 is at 5 volts. The output terminal 326 becomes more negative in response to input signals exceeding 5 volts in a negative direction. The gain control resistor 308 is then set to provide a 10 volt output signal at the terminal 326 in response to the most negative input signal from the rate meter 14. On the other hand, if it is desired to have the output signal at the terminal 326 vary from 5 volts to -10 volts in response to an input signal variation of, for example, from 6 volts to its most negative level, the contrast enhancement potentiometer 320 is adjusted to provide a less negative voltage on the base of the PNP-transistor 322. This requires an input signal that is more negative than 5 volts to produce a 5 volt output signal at the terminal 326. In this manner, input signals, having amplitudes lying within a predetermined portion of the input signal amplitude range are effectively suppressed. In other words, input signals having amplitudes less negative than a predetermined level, produce no output color change. The upper portion of the normal output range of the amplifier is expanded so that the six colors of light which expose the color sensitive film represent less than the entire range of input signal amplitudes.

It is pointed out that the end of the winding of the contrast enhancement potentiometer 320 shown as connected to ground may alternatively be connected to a positive source of voltage (not shown), which will serve to increase the available contrast range.

The derandomizer 70 (FIG. 1) comprises logic circuitry which is shown in FIG. 5. It serves to prevent the overlapping of dots in the colored image produced on the color-sensitive film 94, which might result in producing dark spots on the film. Inasmuch as the derandomizer comprises a plurality of logical elements, each of which is well-known in the art, its particular circuitry will not be described. Reference may be made to any one of a number of various technical publications for descriptions of the circuitry of the various elements, including Department of the Army Technical Manual 'I'Ml l-690, published in 1959.

It is pointed out that all pulses received by, produced within and provided by the derandomizer are below ground potential. In other words, when a positive pulse or a positive-going pulse is mentioned, it means a pulse that starts from a negative potential and rises to ground potential and then returns to its negative potential. Similarly, a negative pulse or a negative-going pulse means a pulse that starts at ground potential, drops to a negative potential and then rises to ground potential at am.

As shown in FIG. 5, positive-going input pulses are received from the one-shot multivibrator 16 at an input terminal 350, which is connected as one input to a NAND-gate 352. The output of the NAND gate 352 is connected as one input to a one-shot multivibrator 354. The multivibrator 354 provides a positive-going pulse to an inverter 356 and a negative-going pulse to an inverter 358 and to one input of a NOR-gate 360.

The negative-going output pulse of the inverter 356 is provided to an output terminal 362, from which it is connected to the gates 64, 66, 68 previously described. The negative-going output pulse of the inverter 356 is also connected to the input of a one-shot multivibrator 364. The one-shot multivibrator 364 is a conventional type in which the width of its output pulse is determined by the discharge time of a capacitor in the multivibrator. In order to discharge the capacitor at various rates, depending on the rate of scan of the probe 10 (FIG. 1 a connection is provided to the multivibrator on a terminal 366 from the speed control circuit 72. The speed control circuit will be later described in detail.

The multivibrator 364 provides two output signals. A positive-going output pulse is coupled through an inverter 368 to one input of a NAND-gate 370. The output pulse from the NAND gate 370 is connected as a second input to the one-shot multivibrator 354.

The negative-going pulse output of the multivibrator 364 is connected as an input to the NAND-gate 352 and as an input to the NOR-gate 360. The output signal from the NOR-gate 360 is connected as one input to a NAND-gate 372, a second input to which is from the input terminal 350.

A negative-going output signal from the NAND-gate 372 is connected to a set input "terminal of a bistable multivibrator 374. A reset input terminal of the multivibrator 374 is connected to receive the positivegoing signal from the inverter 358. A positive-going output signal from the bistable multivibrator 374 is connected as a second input to the NAND-gate 370.

To aid in understanding the operation of the derandomizer, assume first that no input pulses have been received for a time. This means that the output from the NAND-gate 352 to the multivibrator 354 is at ground level, the output of that multivibrator to the inverter 356 is at a negative level, and the output of that multivibrator to the inverter 358 and the NOR-gate 360 is at ground level. It follows that the input to the one-shot multivibrator 364 from the inverter 356 will be at ground level, and the input to the reset terminal of the multivibrator 374 will be at a negative level. The output of the one-shot multivibrator 364 to the inverter 368 will be at a negative level, and the output of the inverter 368 to the NAND-gate 370 will be at ground level. The output of the multivibrator 364 to the NOR- gate 360 and to the NAND-gate 352 will be at ground level. If now a positive-going pulse is received at the input terminal 350, a negative pulse is supplied from the NAND-gate 352 to the one-shot multivibrator 354. The multivibrator 354 provides a. positive pulse to the inverter 356, which inverts the pulse to provide a negative pulse to the output terminal 362 and to the input of the one-shot multivibrator 364.. A negative output pulse from the multivibrator 354 is inverted by the inverter 358 to provide a positive pulse to the reset terminal of the bistable flip-flop 374. A negative pulse is also supplied to an input of the NOR-gate 360 from the multivibrator 354. The one-shot multivibrator 364 does not respond to a negative pulse and so continues to provide a negative voltage to the inverter 368, and ground potential to the NOR-gate 360 and to the NAND-gate 352. The negative pulse applied to the input of the NOR-gate 360 from the multivibrator 354 provides a positive output pulse to the NAND-gate 372. If while the input pulse to the NAND-gate 372 from the NOR- gate 360 is positive, another positive pulse is supplied to the NAND-gate 372 from the input terminal 350, the output of the NAND-gate 372 will be a negative pulse which will set the multivibrator 374 to provide a positive voltage to the gate 370. The bistable multivibrator 374 will then remain in its set condition, regardless of how many pulses are received from the input terminal 350 through the NAND-gate 372, until it has been reset by a positive pulse from the inverter 358.

When the output from the first one-shot multivibrator 354 again goes negative and a positive pulse is transmitted to the second one-shot multivibrator 364, the multivibrator 364 provides a positive pulse to the inverter 368 which in turn provides a negative pulse to one input of the gate 370. A negative output pulse is also provided from the one-shot multivibrator 364'to the NOR-gate 360 and to the second input of the NAND-gate 352. Thus the NAND-gate 352 is closed, and no further input pulses can be supplied to the oneshot multivibrator 354 from the input terminal 350 until the input to the NAND-gate 352 from the oneshot multivibrator 364 again returns to ground potential. It is again pointed out that the output pulses supplied from the second one-shot multivibrator 364 are of variable width, the width of the pulses being determined by adjustmentof the speed control circuit connected to the terminal 366 of the multivibrator. The circuit connection to the terminal 366 provides a path to discharge a capacitor in the multivibrator 364 when the charge on the capacitor has built up to a predetermined value, and thus to end the output pulse from the multivibrator.

When the output pulse from the one-shot multivibrator 364 to the inverter 368 again goes negative, a positive pulse will be applied to one input of the NAND- gate 370. If at this time the multivibrator 374 is in its set condition, a positive potential will also be applied to the other input of the NAND-gate 370, which will cause a negative output from the NAND-gate 370 to be supplied to the first one-shot multivibrator 354. Thus another output pulse will be produced by the one-shot multivibrator 354. If, during the time that either of the multivibrators 354 or 364 was set, no additional pulse is received on the input terminal 350, the pulse supplied to the NAND-gate 370 from the inverter 368 will not go through the gate 370 because the multivibrator 374 will not have been set and its output supplied to the gate 370 will be negative. Therefore, another output pulse will not be obtained from the derandomizer at its output terminal 362 until another input pulse comes in on the terminal 350.

It is apparent that the bistable multivibrator 374 serves in efiect as a memory unit to store one input pulse if the pulse is received on the input terminal 350 before the first one-shot multivibrator 354 is in a condition to be again set, that is, before the end of the negative pulse supplied from the multivibrator 364 to the NAND-gate 352. The inverter 358 supplies a pulse to the multivibrator 374 to reset it at the leading edge of the output pulse from the one-shot multivibrator 354, so that the multivibrator 374 may be again set during the next cycle of operation.

a The speed control circuit which is connected to the terminal 366 of the second one-shot multivibrator 364 in the derandomizer is shown in FIG. 3. It comprises a variable resistor 380 and a potentiometer 382 connected in series between the 24 volt supply and ground. A movable arm of the potentiometer 382 is connected to the base of an NPN-transistor 384. The emitter of the transistor 384 is connected through a variable resistor 386 and a fixed resistor 388 to the 24 volt supply. The collector of the transistor 384 is connected to an output terminal 390, which is connected to the terminal 366 of the multivibrator 364 shown in FIG. 5. The variable resistors 380 and 386 serve only as calibration adjustments.

The setting of the movable arm of the potentiometer 382 determines the potential applied to the base of the transistor 384, and therefore controls the collector current of the transistor. This current controls the widths of the output pulses of the multivibrator 364 in the derandomizer. The arm of the potentiometer 382 may be manually set in accordance with various available scanning speeds of the probe 10, or it may be mechanically linked to the speed control mechanism of the probe. In either case, the potentiometer is so set that when the probe is scanning at a slow rate of speed, the widths of the output pulses from the second one-shot multivibrator 364 are relatively wide. Conversely, if the probe is scanning at a relatively high rate of speed, the widths of the output pulses from the multivibrator 364 may be considerably narrower. In other words, if the probe scanning speed is slow, the potentiometer 382 is adjusted to decrease the collector current of the transistor 384, whereas if the probe scanning speed is relatively fast, the potentiometer is adjusted to provide increased collector current through the transistor. Thus, the capacitor in the one-shot multivibrator 364 is discharged in varying time periods of time depending upon the probe scanning speed.

Although an embodiment of the invention has been shown and described in detail, it is apparent that many changes and modifications may be made by one skilled in the art without departing from the true scope and spirit of the invention.

What is claimed is:

1. In a scintillation recording device including a scintillation responsive means for providing signal pulses at a rate proportional to radioactivity detected, rate detection means connected to the scintillation responsive means for providing a first output signal whose value varies over a first range with the rate of said signal pulses, and amplifier means connected to receive said fust output signal and to provide a second output signal whose value varies over a second range with the rate of said signal pulses, the improvement comprising:

a. first, second and third discriminators connected to receive said second output signal, said discriminators being selectively actuated in response to various values of said second output signal to provide first, second and third energizing signals;

b. first, second and third light sources corresponding to said first, second and third discriminators, each of said light sources being connected for energization to its corresponding discriminator;

c. said first, second and third light sources including first, second and third means for generating light and first, second and third optical means being adapted to direct light from its corresponding source toward a common point; and,

d. each of said light sources being adapted to produce a light which is different in color from that produced by the others of said light sources;

e. whereby one or a combination of said light sources may be energized and the light therefrom transmitted by said optical means to said common point where such light is combined to produce a color indicative of the radioactivity detected.

2. The scintillation recording device of claim 1 additionally including first, second and third gates interposed between said discriminators and said light sources, each of said gates being connected to receive the energizing signal from its corresponding discriminator, and being connected to receive said signal pulses and being operative to energize its corresponding light source upon receipt of an energizing signal.

3. In a scintillation recording device including a scintillation responsive means for providing signal pulses at a rate proportional to radioactivity detected, rate detection means connected to the scintillation responsive means for providing a first output signal whose value varies over a first range with the rate of said signal pulses, and amplifier means connected to receive said first output signal and to provide a second output signal whose value varies over a second range with the rate of said signal pulses, the improvement comprising:

a. first, second and third discriminators connected to receive said second output signal, said discriminators being selectively actuated in response to various values of said second output signal to provide first, second and third energizing signals;

b. first, second and third gates corresponding to said first, second and third discriminators, each of said gates being connected to receive the energizing signal from its corresponding discriminator, and being connected to receive said signal pulses;

c. first, second and third light sources corresponding to said first, second and third gates, each of said light sources being connected for energization to its corresponding gate;

. each of said gates being operative to energize its corresponding light source upon receipt of an energizing signal;

e. each of said light sources being adapted to produce a light which is different in color from that produced by the others of said light sources; and,

f. first, second and third optical means corresponding to said first, second, and third light sources, each of said optical means being adapted to direct light from its corresponding source toward a common point;

g. whereby one or a combination of said light sources may be energized and the light therefrom transmitted by said optical means to said common point where such light is combined to produce a color indicative of the radioactivity detected.

4. The scintillation recording device of claim 3 wherein said optical means comprise fiber optic means for delivering light from said light sources to said common point.

5. The scintillation recording device of claim 3 wherein said light sources individually provide light of three difierent primary colors.

6. The scintillation recording device of claim 3 additionally including aperture means, and said optical means is adapted to transmit light from said sources to a common point within a plane defined by said aperture means.

7. The scintillation recording device of claim 6 wherein said optical means comprise fiber optic means for causing light from said sources to be coincident in said plane defined by said aperture means.

8. The scintillation recording device of claim 7 wherein said light sources are energizable one at a time and in combination to provide a combined light as viewed through said aperture means ranging progressively in color from yellow to red to magenta to blue to cyan to green as the amplitude of said output signals vary progressively from end to end of said first and second ranges, respectively.

9. In a scintillation recording device including a scintillation responsive means for providing signal pulses at a rate proportional to radioactivity detected, rate detection means connected to the scintillation responsive means for providing a first output signal whose value varies over a first range with the rate of said signal pulses, and amplifier means connected to receive said first output signal and to provide a second output signal whose value varies over a second range with the rate of said signal pulses, the improvement comprising:

a. first, second and third discriminators connected to receivesaid second output signal, said discriminators being selectively actuated in response to various values of said second output signal to provide first, second and third energizing signals;

b. first, second and third gates corresponding to said first, second and third discriminators, each of said gates being connected to receive the energizing signal from its corresponding discriminator, and being connected to receive said signal pulses;

c. first, second and third light sources corresponding to said first, second and third gates, eachof said light sources being connected for energization to its corresponding gate;

d. each of said gates being operative to energize its corresponding light source upon simultaneous receipt of an energizing signal;

. said light sources being adapted to produce light of three different primary colors;

f. first, second and third fiber optical means corresponding to said first, second, and third light sources, each of said optical means being adapted to direct light from its corresponding source toward a common point; and,

g. aperture means positioned within a plane including said common point; whereby one or a combination of said light sources may be energized and the light therefrom transmitted by said optical means to said common point where such light is combined to produce a color indicative of the radioactivity detected, and said combined light is transmitted through said aper' ture means. 

1. In a scintillation recording device including a scintillation responsive means for providing signal pulses at a rate proportional to radioactivity detected, rate detection means connected to the scintillation responsive means for providing a first output signal whose value varies over a first range with the rate of said signal pulses, and amplifier means connected to receive said first output signal and to provide a second output signal whose value varies over a second range with the rate of said signal pulses, the improvement comprising: a. first, second and third discriminators connected to receive said second output signal, said discriminators being selectively actuated in response to various values of said second output signal to provide first, second and third energizing signals; b. first, second and third light sources corresponding to said first, second and third discriminators, each of said light sources being connected for energization to its corresponding discriminator; c. said first, second and third light sources including first, second and third means for generating light and first, second and third optical means being adapted to direct light from its corresponding source toward a common point; and, d. each of said light sources being adapted to produce a light which is different in color from that produced by the others of said light sources; e. whereby one or a combination of said light sources may be energized and the light therefrom transmitted by said optical means to said common point where such light is combined to produce a color indicative of the radioactivity detected.
 2. The scintillation recording device of claim 1 additionally including first, second and third gates interposed between said discriminators and said light sources, each of said gates being connected to receive the energizing signal from its corresponding discriminator, and being connected to receive said signal pulses and being operative to energize its corresponding light source upon receipt of an energizing signal.
 3. In a scintillation recording device including a scintillation responsive means for providing signal pulses at a rate proportional to radioactivity detected, rate detection means connected to the scintillation responsive means for providing a first output signal whose value varies over a first range with the rate of said signal pulses, and amplifier means connected to receive said first output signal and to provide a second output signal whose value varies over a second range with the rate of said signal pulses, the improvement comprising: a. first, second and third discriminators connected to receive said second output signal, said discriminators being selectively actuated in response to various values of said second Output signal to provide first, second and third energizing signals; b. first, second and third gates corresponding to said first, second and third discriminators, each of said gates being connected to receive the energizing signal from its corresponding discriminator, and being connected to receive said signal pulses; c. first, second and third light sources corresponding to said first, second and third gates, each of said light sources being connected for energization to its corresponding gate; d. each of said gates being operative to energize its corresponding light source upon receipt of an energizing signal; e. each of said light sources being adapted to produce a light which is different in color from that produced by the others of said light sources; and, f. first, second and third optical means corresponding to said first, second, and third light sources, each of said optical means being adapted to direct light from its corresponding source toward a common point; g. whereby one or a combination of said light sources may be energized and the light therefrom transmitted by said optical means to said common point where such light is combined to produce a color indicative of the radioactivity detected.
 4. The scintillation recording device of claim 3 wherein said optical means comprise fiber optic means for delivering light from said light sources to said common point.
 5. The scintillation recording device of claim 3 wherein said light sources individually provide light of three different primary colors.
 6. The scintillation recording device of claim 3 additionally including aperture means, and said optical means is adapted to transmit light from said sources to a common point within a plane defined by said aperture means.
 7. The scintillation recording device of claim 6 wherein said optical means comprise fiber optic means for causing light from said sources to be coincident in said plane defined by said aperture means.
 8. The scintillation recording device of claim 7 wherein said light sources are energizable one at a time and in combination to provide a combined light as viewed through said aperture means ranging progressively in color from yellow to red to magenta to blue to cyan to green as the amplitude of said output signals vary progressively from end to end of said first and second ranges, respectively.
 9. In a scintillation recording device including a scintillation responsive means for providing signal pulses at a rate proportional to radioactivity detected, rate detection means connected to the scintillation responsive means for providing a first output signal whose value varies over a first range with the rate of said signal pulses, and amplifier means connected to receive said first output signal and to provide a second output signal whose value varies over a second range with the rate of said signal pulses, the improvement comprising: a. first, second and third discriminators connected to receive said second output signal, said discriminators being selectively actuated in response to various values of said second output signal to provide first, second and third energizing signals; b. first, second and third gates corresponding to said first, second and third discriminators, each of said gates being connected to receive the energizing signal from its corresponding discriminator, and being connected to receive said signal pulses; c. first, second and third light sources corresponding to said first, second and third gates, each of said light sources being connected for energization to its corresponding gate; d. each of said gates being operative to energize its corresponding light source upon simultaneous receipt of an energizing signal; e. said light sources being adapted to produce light of three different primary colors; f. first, second and third fiber optical means corresponding to said first, second, and third light sources, each of said optical means being adapted to direct lIght from its corresponding source toward a common point; and, g. aperture means positioned within a plane including said common point; h. whereby one or a combination of said light sources may be energized and the light therefrom transmitted by said optical means to said common point where such light is combined to produce a color indicative of the radioactivity detected, and said combined light is transmitted through said aperture means. 